Calorie restriction—defined as limiting an animal's intake to some fraction of what it would eat given the opportunity to eat without restriction ("ad lib")—has been shown to prolong healthy lifespan, reduce inflammation, increase resistance to cancer growth and more. You can read more about calorie restriction (CR) in this recent Time article.
To achieve these benefits, some people self-impose a calorie intake limit, and various ways of doing this have been endorsed (The Longevity Diet, The CR Way, and Alternate-Day Diet). Different ways of achieving similar results through intermittent fasting have also been suggested, including the Fast-5 Diet, the QOD Diet and Eat-Stop-Eat.
Of these, Fast-5 uses the shortest fasting interval (19 hours) and a regular daily schedule. The results of the alternatives appear comparable, so I suggest people go with whichever option works best for his/her schedule. One of the notable aspects of Fast-5 is the appetite correction that occurs in maintenance phase—people tend to remain at a stable weight without counting calories. In my experience, that level of calorie consumption is substantially lower than what I ate when I was eating on an ad-lib schedule. How much lower? I have to guesstimate because I didn't count calories back then (nor do I now.)
What I eat now seems to average 500-700 calories less per day than what I used to eat when I ate ad-lib with three meals a day. Out of a total calorie intake of 2000-2500 per day, that amounts to a cut of 25-35% per day, which puts it in the realm of significant calorie restriction. Since it's relatively easy to do, Fast-5, which is encouraged for weight loss and weight maintenance, may make anti-aging benefits of CR (and intermittent fasting) accessible to a much broader population than the CR alternatives above, and that would likely help a lot with heart disease and other chronic diseases associated with advancing age. What has your experience been?